The use of arr.fill() method in js

1 Overview

arr.fill() is a new method of ES6.
The fill() method is used to replace the elements of an array with a fixed value.

2 fill()

Syntax: array.fill(value, start, end)
parameters

1. value is required. Filled value.
2. start is optional. Start filling position.
3. end is optional. Stop filling position (default is array.length)
   filling starts from the start position and ends at the end-1 position, excluding the end position.
   Modify the original array directly

3 example

let arr1 = [1, 2, 3, 4, 56, 7, 7, 8, 9];
arr1.fill(4, 2, 5);
console.log(arr1)  //   [1, 2, 4, 4, 4, 7, 7, 8, 9]
let arr2 = [1, 2, 3, 4, 56, 7, 7, 8, 9];
arr2.fill(4);
console.log(arr2)  //  [4, 4, 4, 4, 4, 4, 4, 4, 4]